This invention relates generally to torch equipment for bevel cutting pipe and more particularly concerns a ring gear mounted; rack adjustable torch arm carriage assembly capable of accurately bevel cutting out-of-round pipes.
Pipe cutting torches are generally mounted on either a wheeled carriage which rides directly on the outer surface of the pipe or on a carriage which rides on a ring gear which surrounds the circumference of the pipe.
The wheeled carriage device travels on the pipe. Therefore, out-of-round adjustment is generally unnecessary if it is assumed that the pipe cross section along the path of the wheel carriage is identical to the pipe cross section along the path of the torch. However, adaptation of the wheeled carriage device to a variety of pipe sizes is time consuming and complicated. Furthermore, the tendency of the wheeled carriage device to drift during operation introduces error in the accuracy of the cut. The net result is a comparatively slow and inaccurate cutting operation.
The ring gear carriage devices use a saddle fixed to the outer diameter of the pipe with the ring gear being rotatable around the pipe. A specific saddle and ring gear is used for each diameter of pipe and the carriage is removably mounted to the ring gear. Thus, set-up requires only that the user mount the saddle on the pipe and attach the carriage to the ring gear. Since the carriage travels on the ring gear and not on the pipe surface, extremely accurate cutting is possible at a relatively high speed. However, if the pipe is not round, as the carriage travels on the round ring gear, the distance between the torch and the outer surface of the pipe will vary along the out-of-round pipe. As a result, a torch angled to produce a beveled cut will cause the cut to deviate from the anticipated plane of the cut transverse to the pipe. To overcome this deviation, some known ring gear devices raise and lower the torch radially in relation to the pipe. However, raising and lowering the torch in a radial direction still introduces inaccuracy into the cut if the pipe contour which causes the torch to be raised and lowered is not the same as the pipe contour in the path of the torch. Presently known ring gear devices with out-of-round capability therefore provide limited assistance in maintaining cut accuracy.
A further problem with known ring gear devices with a mechanism for raising and lowering the torch in response to out-of-round contours is that the mechanism is an integral part of the device. A purchaser who may or may not have a need for out-of-round capability in the future must choose whether to buy the considerably more expensive out-of-round equipment which may never be needed or the device that does not have the out-of-round capability. If it is subsequently necessary to buy the more expensive out-of-round device the other device may be useless.
Another problem with known ring gear devices with out-of-round capability is that the structure affording the out-of-round capability complicates the device to the extent that time consuming adjustments are necessary to configure the assembly so as to permit making inverted bevel cuts.
It is, therefore, an object of this invention to provide a ring gear mounted rack adjustable torch arm carriage which bevel cuts round pipe accurately. Another object of this invention is to provide a ring gear mounted rack adjustable torch arm carriage which is adaptable to receive a separate assembly affording out-of-round capability. A further object of this invention is to provide a ring gear mounted rack adjustable torch arm carriage which affords out-of-round capability without radially displacing the torch arm. Yet another object of this invention is to provide a ring gear mounted rack adjustable torch arm carriage which affords out-of-round capability by angular motion of the torch about an axis parallel to the pipe axis. It is also an object of this invention to provide a ring gear mounted rack adjustable torch arm carriage which is rack adjustable to vary the distance between the guide assembly and the torch. Still another object of this invention is to provide a ring gear mounted rack adjustable torch arm carriage which is readily adjustable to permit inverted bevel cuts.
In accordance with the invention, a torch carriage assembly is provided for use in bevel cutting a pipe. A ring gear having a diameter greater than the diameter of the pipe is adapted to be mounted on the pipe for concentric rotation about the longitudinal axis of the pipe. A shaft is mounted on the ring gear and extends perpendicularly therefrom. A torch arm block assembly is fixed on the shaft and adapted to position the cutting torch in relation to the pipe so as to travel a desired cutting path on the pipe as the ring gear is rotated about the pipe longitudinal axis. A shaft mounting bracket is adaptable between a first configuration prohibiting rotation of the shaft about its longitudinal axis and a second configuration permitting rotation of the shaft about its longitudinal axis. In the first configuration the device is usable for bevel cutting round pipes and in the second configuration for bevel cutting out-of-round pipes. When in the second configuration for bevel cutting out-of-round pipes, a guide wheel assembly is also used. The guide wheel assembly is adapted to be mounted on the shaft and has a guide wheel which traces the surface of the pipe as the shaft moves concentrically about the longitudinal axis of the pipe. The guide wheel assembly causes rotation of the shaft and therefor rotation of the torch arm block assembly in response to out-of-round conditions on the surface of the pipe. A tension assembly linking the shaft and the ring gear is adapted to continually urge the guide wheel into contact with the surface of the pipe so that the angular position of the torch arm block assembly accurately reflects out-of-round conditions on the surface of the pipe.